Published patent application US 2005/0263594 of Onischu describes a computerized voting system where ballots are mailed to voters who then exchange ballots before voting. Filled out ballots are then returned to a polling office. The random private ballot exchange decouples the ballot from the eligible voter rolls.
U.S. Pat. No. 7,328,181 to Sutton et al describes a system and method for transacting a purchase using a non-personalized purchase card, the non-personalized purchase card not having any card holder data thereon.
US published patent application US 2004/0111751 of Tsuria describes a method and apparatus for anonymously ordering an item in a pay-per-item system.
Private Web Search with Malicious Adversaries, Lindell, Yehuda, and Wasibard, Erez, in Atallah, Mikhail, ed. Privacy Enhancing Technologies (Lecture Notes in Computer Science, Vol.: 6205), Springer Berlin/Heidekberg 2010, pp. 220-235.
The Fiat-Shamir identification scheme is a type of parallel zero-knowledge proof that allows a first party to prove to a second party that the first party possesses secret information without revealing to the second party what that secret information is. It was described by Feige, Fiat and Shamir in “Zero-Knowledge Proofs of Identity,” Journal of Cryptology 1:2 (1988).
Anonymized tokens are discussed in the following references:                D. Chaum, Blind signatures for untraceable payments: CRYPTO '82, p. 199-203. Plenum Press, 1982;        D. Chaum. Security without Identification: Transaction Systems To Make Big Brother Obsolete: Communications of the ACM, 2 8(10):103 0-10 44, October 1985; and        D. Chaum, A. Fiat, and M. Naor. Untraceable Electronic Cash: CRYPTO, volume 40 3 of LNCS, p. 319-327, 1990.        
U.S. Pat. No. 4,759,063 to Chaum describes blind signature systems.
Blind Signature Schemes are also described in An ECC-Based Blind Signature Scheme of Jeng, Chen, and Chen, Journal of Networks, Vol. 5, No. 8, August 2010, available on the World Wide Web at ojs.academypublisher.com/index.php/jnw/article/viewFile/0508921928/2053.
The anonymous communications protocol Crowds is described in Crowds: Anonymity for Web Transactions, Michael Reiter and Aviel Rubin (June 1998). ACM Transactions on Information and System Security 1 (1). The article is available at avirubin.com/crowds.pdf.
The anonymous communications protocol Tor is described in Tor: The Second-Generation Onion Router, Dingledine, Roger; Mathewson, Nick; Syverson, Paul (13 Aug. 2004). Proc. 13th USENIX Security Symposium. San Diego, Calif. The article is available at www.usenix.org/events/sec04/tech/dingledine.html.
The anonymous communications protocol I2P (Invisible Internet Project) is described at www.ip2.de/techintro.html.
Financial Cryptography, International Conference, 1997, Gabber E et al., How to Make Personalized Web Browsing Simple, Secure, and Anonymous, describes a system for anonymous web browsing.